PIN AS 3483889 - Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with the engine fan control solenoid. Also use this procedure if one of the diagnostic codes in Table 1 is active.
Table 1
Diagnostic Codes Table
CDL Code Code Description Comments
291-5 Engine Cooling Fan Solenoid : Current Below Normal The Electronic Control Module (ECM) detects an open circuit in the circuit for the engine fan control solenoid.
The ECM sends minimum current to the fan control solenoid. The code is logged.
291-6 Engine Cooling Fan Solenoid : Current Above Normal The ECM detects a short circuit to ground in the circuit for the engine fan control solenoid.
The ECM sends minimum current to the fan control solenoid. The code is logged. The ECM monitors engine coolant temperature, intake manifold air temperature, and hydraulic oil temperature. The correct speed for the engine cooling fan is then determined.The ECM controls the speed of the fan by controlling the current to the engine fan control solenoid. The engine fan control solenoid controls the amount of pressure to the fan pump by allowing oil to bypass the fan pump. The fan pump drives the fan. The ECM outputs minimum current to the engine fan control solenoid in order to bypass less oil. The fan pump will then drive the fan at a higher rpm. The ECM outputs maximum current to the engine fan control solenoid in order to bypass more oil. The fan pump will then drive the fan at a lower rpm.If the ECM detects a system fault, the ECM provides minimum current to the solenoid. The fan speed will be at maximum while the fault condition exists.An override is available with Caterpillar Electronic Technician (ET). The fan can then be manually changed from the minimum to the maximum rpm.
Illustration 1 g02061556
Schematic for the engine fan control solenoid
Table 2
Troubleshooting Test Steps Values Results
1. Check for Active Diagnostic Codes
A. Turn the keyswitch to the OFF position.
B. Verify that the solenoid connector is free of debris and connected securely.
C. Connect Cat ET to the service tool connector.
D. Turn the keyswitch to the ON position.
E. Select diagnostic tests from Cat ET.
F. Select the "Override Parameters" screen on Cat ET
G. Activate the fan override.
H. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes.
Note: Wait at least 30 seconds in order for the diagnostic code to become active.
I. Disable the fan override.
Codes
Result: No diagnostic codes are active.
Repair: The problem may have been related to a faulty connection in the harness. Carefully inspect the connectors and wiring. Refer to Troubleshooting, "Electrical Connectors - Inspect".
STOP
Result: A short circuit diagnostic code -6 is active at this time.
Proceed to Test Step 2.
Result: An open circuit diagnostic code -5 is active at this time.
Proceed to Test Step 3.
2. Disconnect the Connector for the Engine Fan Control Solenoid to Create an Open Circuit
A. Turn the keyswitch to the OFF position.
B. Disconnect the connector for the engine fan control solenoid.
C. Turn the keyswitch to the ON position.
D. Activate the fan